Benchmarking PCs, Capture Cards, and Software Mixers for HD Capture and Streaming

The Software Factor

How does software change the equation? Have a look at Figure 2 (below), which shows vMix Pro running a similar suite of tests. As you can see, vMix was more efficient than Wirecast across the board, though the advantage dropped from 15–20 percentage points with 7.0.0 to 5–10 percentage points with 7.1. As mentioned previously, the vMix tests are slightly different due to the different archival formats offered by the two programs, including a high-quality but high-data rate YUV format. If you’re running on a slower notebook and CPU utilization is running high, vMix is definitely a viable option. Another option is the free OBS, which is fine for a simple project such as this. It consumed about as much CPU as vMix in live streaming and archiving trials.

Figure 2. CPU utilization for vMix Pro on a 2.8GHz HP ZBook connecting via the Epiphan AV.io 4K video grabber. Click the image to see it at full size.

The other takeaway from working with a USB-based capture system is the need to manage your ports carefully. The ZBook comes with three USB ports, and if you add a portable USB 3.0 drive to store the archive version, placing it in the wrong port can flood the connection. Overall, you’re best off buying a system with sufficient internal storage for a completed event to avoid contention issues.

For those interested in 1080p streaming, I tested streaming to Facebook Live at 1080p@4.5Mbps using Wirecast 7.1. Streaming-only consumed about 25% of total CPU, up from about 18%. With vMix, the bump was similar, from about 15% to 25%.

I ran a similar suite of tests on a MacBook Pro powered by a 2.8GHz Intel Core i7 CPU with Wirecast 7.0.1 and OBS (vMix doesn’t have a Mac-based mixer), but I had to return the MacBook Pro before I received the Wirecast 7.1 upgrade. Mac performance was similar to that achieved on the ZBook in Windows, and I would expect the Wirecast performance improvements found in Windows to extend to the Mac.

On the other side of the coin, I tried duplicating these tests on a Dell Inspiron notebook powered by an i5-4210U CPU, with a base frequency of 1.7GHz and a top speed of 2.4GHz. Note that the i5 has two cores (four with HTT), rather than four on the i7 (eight with HTT), so in addition to the slower speed, there are fewer cores. On the Dell, streaming only at 720p flatlined the CPU at 100%, and even dropping resolution to 360p still resulted in peaks well over 90%. Though it might be feasible to stream from an i5 with a faster clock speed, if you’re buying new, go for an i7 or four-core (eight with HTT) Xeon-based system.

Mixing It Up With the AJA Io 4K

Epiphan’s AV.io 4K is an affordable single-stream product, but what about multiple-camera productions on a notebook? While you can hang multiple single-stream capture devices from your notebook, you’ll get the most efficient results with a product like AJA’s Io 4K, which supports up to four 1080p inputs and connects via Thunderbolt 2.

To test the Io 4K, I used the Osprey SDARD-4 Distribution Amplifier, which inputs a single HD-SDI stream and outputs four, connected to the Io 4K. I used the same AVCHD source video, converting that to HD-SDI with a Blackmagic Design Mini Converter HDMI to SDI. The procedure was the same, except during playback. I cycled through the four inputs in Wirecast and vMix every 5 seconds or so. As shown in Figure 3 (below), the results were pretty phenomenal, with vMix supporting live four-camera mixing and x264 archiving while consistently below 60% CPU utilization. Even compared with the new Wirecast version 7.1, vMix proved about 10% more efficient than Wirecast in all operations. Again, performance on the MacBook Pro matched that in Windows with Wirecast version 7.0.1.

Figure 3. CPU utilization for vMix on a 2.8GHz HP ZBook connecting via the AJA Io 4K video grabber

These results seemed almost unrealistically positive, so I hunted around to see if I could find confirming results. I found one producer on the Telestream boards who reported 80%-plus CPU utilization on a 3GHz i7-based 13" MacBook Pro Retina, though actual details about the production are limited and the producer was very positive (“CPU was 80%+ but that was with 4 cameras in one shot. This is a great solution …”). There’s also a YouTube video available at bit.ly/2bDcZ6P that shows the MacBook Pro/AJA setup working, though CPU utilization details are lacking.

I asked AJA about minimum system requirements for the Io, and the company deferred to the requirements of the software program. I checked the vMix website, which recommends a 3GHz+ i7 with 8GB of RAM, while Telestream recommends a similar configuration for 1080p streams. My tests on the 2.8GHz systems indicated that there was little CPU headroom, and I wouldn’t recommend producing on anything slower than our tested systems.

On the other hand, I’m sold on Thunderbolt-based mobile productions for systems that support it. Note that the ZBook offers two Thunderbolt 3 ports, but no Thunderbolt 2 ports. The price for this future-proofing is that you’ll need a Thunderbolt 3-to-Thunderbolt 2 dongle. I used the StarTech Thunderbolt 3 to Thunderbolt Adapter, which costs about $75. While the dongle worked fine with the AC-powered AJA unit, it did not work with my Thunderbolt 2 external SSD drive, though the specs say it does pass power through to bus-powered devices.